Method of separating tall oil into a fatty acid product and a rosin acid product



Sep. 7, 954 E. F. slssoN ET A1.

METHOD OF SEPARATING TALL OIL INTO A FATTY ACID PRODUCT AND A ROSIN ACID PRODUCT 5 Sheets-Shes?l l Filed DeC. 13, 1947 All NQS: la

EVENT-DPE daba f? Kawai/N Sept. 7, 1954 E. F. slssoN Erm.

METHOD oF SEPARA TING TALL OIL INTO A FATTY ACID PRODUCT AND A ROSIN ACID PRODUCT 5 Sheets-Sheet 2 Filed Dec. 13, 1947 "fill Iv HN@ liv WmGnS 589i 7, 1954 E. F. slssoN ET A1.

METHOD OF SEPARATING TALL OIL INTO A FATTY ACID PRODUCT AND A RosIN ACID PRODUCT 5 Sheets-Sheet 3 Filed Dec. l5, 1947 .2-2.1751275215 [ami/va F J/No/v Sept. 7, 1954 E. F. slssoN ET AL 2,688,590

METHOD OF SEPARATING TALL OIL. INTO A FATTY ACID PRODUCT AND A RosrN ACID PRODUCT Filed Deo. 13, 1947 5 sheets-sheet 4 P 2.31. 7 FIRST sEP CYCLE nu. olL

FEED TALL 0"- RoslN @cms 5s FATTY ACIDS 3s 7o Ti (M E. U. 9 72| gtme l wwon- GONDENSER Evwosmron '-WD 33 summon com 55 um: REcYcLE cooLEn 5T alumnus lsf I In" :al Malou: j! l Y CYCLE $2 DAME As cvcLE T L- er man. i DlsrlLLATE ZZ Tm ad Rosm Amos 3M ,m w FATY @cms 69% f "m1-m E.& U. 3% a erasmus F l I n J Y CYCLE $3 DAME Aa cYcLE l l Fain: a-DasraLLATE y Ja s'uaaslaua Rosm Amos am FATTY Dems mi, "wf-TE a. D u. 5% i J v; CYGL Sams as cvcLa 1 8f Fain: s DasTlLLmE v 4f mxslnuz '4TH Rosl Aclns s #o Mmmm PATTY GIDS 84 fa Il E. U. T "fa Y DD seDDmD SWP Edmond F saazz Fia/mrd C70/6 E. F'. SISSON ET AL METHOD OF SEPARATING TALI.. OIL INTO A F'ATTY Sept. 7, 1954 5 Sheets-Sheet 5 Filed Dec. l5, 1947 CIJQQu www :n.w H 0 ma@ mi .1.21 El@ d? H m M www@ 4 l0 .1. M 55u :groin 03:52.: u n.. ...am M a nu .u s o .m (\\lwm. 9w om u /W 3.-:- zor-.oum .J 22....: 5232.3 ..:.uu.. .Ill wmvww 7W u ms 9.52.. m 2. w20@ .CL mw. w @n n.2 z wo..

oww,... 7: m .W El m5 028mm Y Patentecl Sept. 7, 195,41

METHOD OF SEPARATING TALL OIL INTO A FATTY ACID PRODUCT AND A ROSIN ACID PRODUCT Edmond F. Sisson, Richard F. Cole, and Jacob P.

Krumbein, Pensacola, Fla., assignors to Newport Industries, Inc., Pensacola, Fla., a corporation of Delaware Application December 13, 1947, Serial No. 791,490

4 Claims.

This invention relates to a method for the separation of a mixture of organic chemicals into its component fractions, and more particularly to the separation of tall oil into a fatty acids product and a rosin acids product. It should be understood, however, that the method herein described is applicable to the separation of any mixture of a high molecular weight fatty acid, such as oleic acid, and any other acidic compound, such as a rosin acid, into a relatively pure fatty acids product and a relatively pure rosin acids product.

Tall oil is the natural mixture of rosin acids, fatty acids, and of non-acid bodies which is obtained by the acidification of the skimmings of the black liquor of the alkaline paper pulp industry. Skimmings is the name applied to the curd, before being acidiiied or otherwise processed, which is skimmed from the black liquor of alkaline pulping processes. The crude tall oil, which is obtained by acidification of the skimmings, may be refined either by vacuum distillation of the crude tall oil or by processing the crude tall oil with fullers earth, or by combinations of these steps. Any satisfactory refining operation should remove a large proportion of the color bodies and of the non-acid bodies present in the crude tall oil.

The composition of refined tall oil will vary appreciably, depending upon the producer of the black liquor, although it will usually fall within the ranges tabulated below:

Percent Rosin acids 45 to 60 Fatty acids 35 to 50 Esters and unsaponifiables 6 to 12 By the method of the present invention the refined tall oil is separated into a rosin acids fraction containing 9% or less of fatty acids, a fatty acids fraction containing approximately 95% fatty acids and 5% rosin acids, and an unsaponifiable by-product fraction containing a minimum of 75% unsaponifiables.

The separation of refined tall oil by ordinary,

methods of fractionation is difcult to achieve, due to the fact that the rosin acids and, to a lesser extent, the fatty acids, are heat-sensitive materials which decompose when heated to tem-A 260 C., with resultant high rates of decomposition. Also, with conventional vertical or horizontal tube evaporators which supply the necessary heat to perform the desired fractionation, there exists a liquid head of from 1 to 10 feet in the zone of boiling liquids in the evaporator. Hence, the bubbles of vapor are generated at approximately 20 to 200 mm. mercury pressure above the pressure in the vapor space, which in turn requires that the liquid be heated to a higher temperature in order to effect vaporization. This higher temperature, of course, results in higher rates of decomposition.

The process of the present invention eliminates these undesirable features of previous processes by performing the rosin acids-fatty acids separation in four separate equilibrium vaporization steps at below 5 mm. Hg pressure, utilizing a falling film evaporator which vaporizes the liquid at a liquid head of less than 5 mm. as compared with l to 5 or even 10 feet in the conventional tubular type evaporator.

The final fatty acids product from the fourth vaporization is fractionated in a packed column which utilizes a porcelain type packing material for promoting intimate contact between the ascending vapors and descending liquids, as differentiated from the conventional bubble cap fractionating column with heat exchange zones. The advantages of a packed column with respect to a bubble cap column are that the pressure drop between the upper and lower sections is reduced by at least 50%, and the fractionating efficiency for a given size is often greater than that for a comparable bubble cap column.

More specifically, the process of the present invention may be divided into two steps, the first of which comprises performing a preliminary rough separation of the rosin acids and fatty acids constituents of the tall oil in four successive equilibrium vaporizations, and a second step which comprises refining the fatty acids in the distillate from the fourth vaporization. This latter consists in first removing the unsaponifiables fraction and concentrating the same, and secondly, in distilling the residue from this latter step to produce a highly refined fatty acids product.

In the performance of the first rough separation step, the refined tall oil is pumped from a storage tank through heat exchangers which heat the oil to approximately C. After passing through the final heat exchanger the oil is passed to the top of a tubular falling film evaporator. A portion of the tall oil is vaporized in the falling film evaporator, and both the vapor and unvaporized feed are passed to a separator. In the separator, the vapor and liquid phases are disengaged and the vapor is condensed and subcooled. The non-condensables from the condensers are fur- 3 ther cooled and finally exhausted bya three-stage steam jet vacuum pump operating at less than 5 mm. mercury absolute pressure.

The combined condensed distillate flows into a plurality of receivers, maintained at 8 inches mercury absolute pressure, through a liquid seal. The function of the liquid seal is to permit the collection of the distillate at the relatively low vacuum of 8 inches mercury absolute pressure instead of the 3 to 5 mm. at which the evaporator operates. This feature permits the location of process valves at points where air leakage through the packing glands can be exhausted by the low vacuum high capacity pump. This in turn reduces the duty of the high vacuum low capacity lpump which maintains the desired vacuum at the evaporator. The distillate is dropped by gravity from the receivers to a storage tank. The unvaporized tall oil from the evaporator is pumped from the liquid-vapor separator through a cooler intoI receiving tanks. A portion of the unvaporizedoil from the separator is recycled through the falling film evaporator so that the inside surface of the tubes may be continuously wetted, and the volatile constituents further removed from the oil.

In the first equilibrium vaporization, the portion of feed stock vaporized'is such as to produce a residue and distillate of the following composition:

Distillate Residue Percent Percent Rosin Acids 37 75 Fatty` Acids 60 9 Esters and Unsaponiflables; 3 16 Distillate Residue Percent Percent Rosin Acids 17 56 Fatty Acids 78 35 Estere and Unsaponiflablcs 5 9 The distillate from the second vaporization comprises the feed stockfor the third. vaporization. The sequence of operations is identical with those described above except that again the distillate is accumulated in a diierent storage tank, and the residue is combined with the dis.- tillate of the iirst vaporization. The composition of the distillate and residue thus obtained is:

Distillate Residue Percent Percent Rosin Acids 9 37 Fatty Acids 84 60 Esters and Unsaponifiables 7 3 T he distillate` ofl the third vaporization comprises the feed stock'for the fourth vaporization'. The sequence of operations is identical with those'4 described above except that` therdistillatefis ac-` 4. cumulated in a different storage tank and the residue is combined with the distillate of the second vaporization. The composition of the distillate and residue from the fourth vaporiza- The four vaporization operations above described comprise the rst integral step of this process, namely, the concentration of rosin acids in the refined tallV oil separately from the fatty acidsA and unsaponiables by four successive equilibrium vaporizations conducted at an absolute pressure of lless than 5 mm. of mercury and at a liquid head of less than 10 mm. inra falling nlm evaporator. Afatty acids-enriched distillate is thereby obtained containing at least 85% of fatty acids, not. over 5%. of rosin acids and not over 10% of unsaponiables.

The distillate from thefourthv vaporization is now submitted to the second integral step. of the process, of the present invention. The distillate from the fourth vaporization ist pumped through one ormore preheaters; and: introduced into a vertical fractionatingA column at approximately the middle location of the column. The frac-- tionating column is of the packed type utilizing a suitable packing material, and is divided into two sections, namely., a stripping; section anda rectifying section.. The. stripping section, located in the. lower portion of thecolumn, serves` to remove virtually allzofV the unsaponiables from the feed stock, .whiley the rectifying section serves to concentrate the. unsaponiable. The rectifying section is located in, theupper half of the column. The, absolutepressure. at the top. ofthe column is maintained at 5 mm. or less, while that. at the bottom isimaintained; atzzi): mm. or less.

The'feed stock is introducedonto a plate tterl withV--notch weirs and flows*` down the stripping section of the column, countercurrent to4 rising vapors. The liquid accumulating in the bottom of-'fthecolumn is recycled into a falling lm evaporator which vaporizes a portion of' the liquid andV providesl the necessaryheat to fractionate the feed stock.- The overhead vapors' from the. fractionating. column, are condensed and a portion. thereof returned to the top of-the column as reflux. The non-condensables are cooled and removedv from the system by a threestage steam jet vacuum1 pump at 5; mm.,mercury absolute or less. That portion of the distlllate not returned as refiux. isv accumulated in areceiver operating at 8 inchesv mercury absolute pressure. From the receiverT the distillate is dropped. intoa storage tank.

Theffc'omposition of, the'` distillate and residue from the fractionating column is as follows: They distillate contains unsaponiables, 25% fatty acids andpractically 0% rosin acids: the residue contains 94% fatty'acids, 5% rosinacidsz and a maximumrof 1% unsaponiiables.

A portionLof the.- liquid drawn from-the'bottom of thefractionatingcolumn ispumpedy to a flash tower operating atv 5 mm. or less mercury absolute pressure, where anmajor, proportion: of` theing the fatty acids: product, from-the ash tower iscondensed-Land accumulatedinfa receiver. The:

residue from' the flash tower is accumulated in a receiver and returned to the first phase of the process rfor reworking.

The composition of the distillate from the flash tower is as follows: a minimum of 95% fatty acids, a maximum of 4% rosin acids, and a, maximum of 1% unsaponinables. The residue from the fiash tower contains approximately equal portions of rosin acids and fatty acids.

Thus it may be seen that we have provided an efficient process for the separation of a mixture of fatty acids and rosin acids into component parts.

It is, therefore, an important object of the present invention to provide an improved method for the separation of a mixture containing high molecular weight fatty acids and rosin acids into its component fractions.

It is a further important object of this inven tion to provide a novel and improved method for effecting a separation of a mixture of high molecular weight fatty acids and rosin acids by a combination of vaporization and fractionation steps carried out under such high vacuum as to prevent any substantial decomposition of the heat sensitive rosin acids.

It is another important object of the present invention to provide for the separation of rened tall oil into two fractions, one of which contains at least 95% fatty acids and less than 5% rosin acids.

It is a still further important object of the present invention to provide an improved method for the separation of tall oil into its component fractions, which method employs a falling lm type of evaporation under absolute pressures of less than 20 mm. Hg to vaporize the volatile constituents of the tall oil.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings, in which:

Figures 1 and 2 together constitute a complete flow sheet presenting a schematic illustration of the complete process of the present invention;

Figure 3 is an elevation, partly broken away and in section, of the tubular vertical falling lm evaporator for use in the method of the present invention;

Figure 4 is a sectional view taken substantially along the line IV-IV of Figure 3;

Figure 5 is a top plan view of the upper end of one of the pipes of the tubular vertical falling nlm evaporator illustrated in Figure 3; and

Figure 6 is a fragmentary elevational view of the upper end of the pipe illustrated in Figure 5;

Figure 7 is a block diagram illustrating the first step of the method of our invention, comprising cycles numbers l to 4, inclusive; and

Figure 8 is a block diagram illustrating the second step of the method of our invention, starting with the fourth distillate of cycle No. 4 of the rst step as the feed for the second step.

In the block diagrams the same reference numerals are used to refer to the same pieces of equipment as are used for such pieces of equipment in Figures 1 to 6, inclusive, of the drawings. The symbols E. & U. in these block diagrams indicate esters and unsaponifiables; the term R, A. is an abbreviation for rosin acids, and the term F. A. is an abbreviation for fatty acids.

With reference to the flow sheet diagrams of Figures 1 and 2, refined tall oil, assumed to consist of 56% by weight of rosin acids, 35% fatty acids, and 9% esters and unsaponlables, is

' into outlet chamber 203.

stored in tank I2 (Figure 1)`. The oil is drawn from the storage tank 'I2 through lines 'I3 and I3, the valve I9 being open, and pumped by means of pump 20 through lines 2I and II to a steam heated exchanger I8. Alternatively, the tall oil may be drawn by pump I5 from tank I2 by opening valve I4, and pumped through line I6 and line II into the heat exchanger I8. 'Ihe oil is heated in the heat exchange I8 to a temperature of approximately C. The heated oil is then pumped through line 22 to a combination heat exchanger and condenser 24.

Alternatively, the heated oil from the heat exchanger I8 may be recycled through line 23 to either of the pumps 20 or I5 to be reheated in the heat exchanger I8.

The oil which has been heated in the heat exchanger IB is further heated in apparatus 24 to a temperature of C. by condensation of vapors as will be explained hereafter. The

heated oil at a temperature of 190 C. is pumped u from the apparatus 24 through line 25 to the top of a vertical falling film tubular evaporator 26.

The tubular evaporator 26 (Figure 3) comprises an inlet chamber 20I, a heat transfer chamber 202, and an outlet chamber 203. The inlet chamber 20| is cylindrical in shape having a generally upwardly dished upper end 204. An inlet pipe 205, centrally located at the top point of the upper end 204, extends through the upper end 204 into the interior of the inlet chamber 20 I. A steel ring 206 is xedly attached, as by welding, to the lower extremity of the Walls 20m of the cylindrical section of the inlet chamber 20|. The ring 206 is of the same inside diameter as the in-l let chamber 20| and is of greater outside diameter. A depending annular flange 201 is provided around the outer periphery of the ring 206 for a purpose to be hereafter described. The cylindrical heat transfer chamber202 is defined by walls 202a and identical circular plates 208 and 209. The plates 208 and 209 are of a diameter greater than that of the chamber 202 proper and are provided with annular grooves 208D and 2091 which are of substantially the same dimensions as the annular flange 201 of ring 206 to receive said flange. A plurality of vertically aligned holes 208@ and 209e are drilled through the plates 208 and 209, respectively, within that portion of each plate which lies within the chamber 202. Pipes 2I0 are inserted into the holes 208a and 209a and held therein by conventional means, as by rolling, so that the pipes 2I0 extend through chamber 202 into inlet chamber 20| above plate 208 and below plate 209 Only one pipe 2I0 is shown in Figure 3, the plan arrangement of the pipes 2I0 in the chamber 202 being shown by Figure 4.

The upper extremities of the pipes 2I0, which extend into the inlet chamber 20|, are formed as shown in Figures 5 and 6. The wall 2 I0a of each pipe is radially cut along a straight line 244 extending downwardly from the upper edge on the pipe surface at an angle of approximately 60. A second radial cut is made along line 243 at an angle of approximately 45 from the same edge of the pipe, the second cut joining the rst at a point below the upper edge of the pipe to define a cut-out angle of approximately 15. A cut-out 2I I is thus provided in the upper section of each pipe 2I0. That section of the pipe directly above the cut-out 2| I is then bent to provide a surface 2 I2 which extends tangentially beyond the circumference of the pipe 2I0. Four such cut-,out

portionsl 2|'I are provided las 'shown in Figure 5. Each of the-cut-out portions 2| is diametrically opposed toanother'portion 2 I I. A stainless steel wire\-2|3 lis secured to the inside'surface'ZM of each pipe 2|0 at the apex 2|5 of eachy of-thecutout portions 2| I and extends helically around the inside surface 2M of the pipe 2|||` for'thefull length thereof and is secured thereto atpoints spaced therealong. A wire 213 is attached at each of the apices 2|5 provided on each pipe 2 I0. The methodof winding the wire 2|3 is shown in Figure 6, only one ofthe four such wires being illustrated.

The heat transfer chamber 202 (Figure 3) carries two flanged nipples 2 |1 and 2 I8 which extend outwardly from the wall 202a of the'chamber 202. Nozzle 2|1 is positioned slightly below plate 208 and` nozzle 2| 8 is positioned slightly above plate l209. A vertical baille plate 2|9 is positioned directly inside the nozzle 2I1 within the chamber 202.

The plate 2|9 is rectangular and is weldedI to the wall 202a of chamber' 202. Two internally threaded `pipe fittings 220 and 22| are positioned on wall 202a opposite the nozzles 2`I1 and 2|8. Fitting 220 is positioned slightly above the extended axis or nozzle 2 |1 and fitting 22| is slightly below the nozzle 2|8. An expansion joint 222 is provided in the wall 20201l of vheat transfer chamber 202.

The expansion joint 222 may be conveniently provided by making the chamber 202 in two cylindrical sections and welding to the ends thereof flared annular portions 223 and 224, respectively,` which' are then welded to each other to form an enlarged diameter expansion joint.

The outlet Uchamber 203 is cylindrical in shape andV provided with a downwardly dished lower end portion 225. An outlet nozzle 22B extends from the lowest portion of the end 225. A side outlet nozzle'221 is provided for the chamber 203 invertical alignment with nozzles 2|1 and 2|8.

The cross-sectional area of outlet nozzle 221 is substantially greater than the cross-sectional areas of nozzles 2|1 and `2I8. A baille plate 228 is provided in the outlet chamber 203 attached to the wall 203a at a point above the outlet nozzle 221 and extendingobliquely and downwardly approximately half-way across the chamber 203.

The outlet chamber 203 is provided at its upper end with a steel ring 229which is identical with ring 206 of chamber 20|. Thering 229 is axed to the upper extremities of wall 203a of chamber 203 with an annular flange 230 extending upwardly from the ring 229.

The shells forming the chambers 20| and 203 are fastened to the shell forming the chamber 202 by means of collars 23| and 232. Bolts 231 and 238 pass through registering holes in the plates 208 and 209 and in collars 23| and 232, securely fastening the chambers together to form the evaporator 26.-' Circularresilient gaskets 24| and 242 fitting into channels 208D and 2091) in plates 208 and 209, respectively, provide seats for the flanges 201 and 230, respectively, to form a vacuum tightseal between the chambers 20|, 202 and 203.

The heated liquidat a temperature. of 190 C. enters the evaporator 26 through line 25. The evaporator is operated at an absolute pressure of less than mm. Hg and preferably at about 3 mm. Hg. The oil passes through inlet pipe 205 onto the upper `surface `of plate 208 and rises within the inlet chamber to the level of the apices-2|5 of the cut-out portions, or weirs, 2|I. The oil flows into the Vpipes 2|0 along the wires 8, 2 I3t'ofb'ef-spread evenly infvthin layers along the innerfwalls`s2|4r=of said pipes 2|0. The volume rate of flow of feed stock is so regulated that at all'times theliquidisfbeing vaporized` at a liquid head less than 5mm.

Alvaporizedheatvtransfer medium, such as a mixture--of'diphenyland diphenyl oxide, is fed from: line/21 'intothe-nozzle 2|1 at a temperature of approximately 275 C. The baille plate 2|9 aidsindistributing the heat transfer medium through thespaces provided between the pipes 2li);l Theesensible Yand latent heat liberated by the condensation of the heat transfer medium within chamber-202 is employed to vaporize the more Vvolatile"constituents -of the oil flowing as thinillms'throughthefpipes 2| 0. The condensed heatf transfer medium-is removed through the/ outlet nozzle 2 I8 to be reheated and after being vaporized' is'again'admittedr through inlet nozzle 2 I1.y The'temperature'of the'evaporator is regulatedby thermocouples (not shown) located in theseparatorZS; The-thermocouples control the amount of heat'transfermedium admitted to the evaporatorl through `valve 2Gb as shown in Figure 1.

The liquid-vapor mixture flows through pipes 2 |`0. Vapor andentrained liquid ilow out through the outletnozzle 221," while non-vaporized liquid ows'out through nozzle 220. Both streams flow tothe'vapor-'liquid separator 29,'through lines 28 and 26a respectively.

The vapor-liquid vseparator 2S is maintained at a pressure of less than 5 mm. Hg. The vaporliquid mixtureis separated in the separator 29, the liquid passing through line 49 as will be hereafter described, and the'vapors, which are considerably richer in' fatty' acids than the liquid, passing through line 30 to the combination condenser-heat exchanger" 24 and condenser 3|. The pressure within' the heat. exchanger-condenser24'and-corrdenser 3| is also maintained at less than 5 mmjllg. The latent heat of vaporizationgiven up' bythe vapors passing through the condenser '24isutilized to heat'th'e oil entering the combination condenser-heat exchanger 24 through. line 22" and leaving the apparatus through line.25; Some of the uncondensed vapors passing through apparatus 24 are condensed in condenser 3|. The condensate from condenser 3| is passed through line 32` and subcooled in a cooler 33.

The lquid'from cooler 33 passing to receivers 36 and 39through-line 34 ows through a U-tube seal whichenables receivers 36 and 39 to operate at an absolute pressure of 8 inches Hg. The liquid may be passed into receiver 36 by closing valve. 38,and .opening valve 35, or the liquid may be passed to the receiver 39 by closing valve 35 and openingyalve 38'. When a desired quantity oflquidhas beenaccumulated in the receivers 36 and 39.the vacuum is removed by release of air vent 31 or 49. Valves 54 are opened and the liquid passes .through lines. 54a and 11 and valve 19 to storage tankrl.

Uncondensed vaporsv from the condenser 3| are drawn .through linef44'tobe subcooled in a cooler 45. Condensed vaporsfrom cooler 45 are introduced intothe. main streamin line 34 through line 48, anduncondensable vapors from cooler 45 are drawn through line 46'by-a three-stage steam jet vacuum pump 41. and. exhausted from the system.

A portionA of the liquid', which is lean in fatty acids, fromv the separator'ZS is passed through line'49; pumpf50- and line vthrough line 52 into a cooler 53. Liquid passing through the cooler 53 is withdrawn through line 53a and passed into tank 59 or 56. The liquid may be passed into tank 56 by closing valve 58 and opening valve 55, or into tank 59 by closing valve 55 and opening valve 58. The receivers 56 and 59 are maintained at a vacuum of 8 inches of mercury by a steam jet vacuum pump 43 which is connected to the receivers through lines 4I and 42. When a sufiicient amount of residue has accumulated in receivers 56 and 59, the pressure therein may be brought to atmospheric pressure by means of air vents 51 and 69 respectively, and either or both of` valves 6I may be opened to allow the liquid to flow through lines 62 and 63 to tank 64.

The amount of liquid being pumped to the receivers 56 and 59 is regulated by a liquid level ccntrol Ia located in separator 29. The control 5 Ia controls valve 5Ic by a connection Eloi. Should the liquid level in separator 29 fall below a predetermined level, valve 5Ic is opened, allowing liquid from separator 29 to be recycled through line 5I to the top of the evaporator or by-passed through line 5Ib to the separator 29. The rate of liquid collection in receivers 56 and 59 is determined by the level of liquid in the separator 29.

This completes one cycle of the operation. The residue collected in this first cycle comprises 9% fatty acids, 75% rosin acids and 16% esters and unsaponii'lables. The distillate which is stored in tank I9 contains approximately 60% fatty acids, 37% rosin acids and 3% esters and unsaponiables. This distillate is again processed in a manner identical to the above described operation by allowing the liquid to ilow through line I2 into line I3 and thence through the same cycle previously described. The distillate, which is again collected in receivers 36 and 39 is this time dropped to tank 89. The collection in tank 89 is accomplished by the venting of tank 36 and 39 as before described, the opening of 'valves 54 allowing the liquid to flow to line 11, and the opening of valve 8| allowing the liquid to flow into tank 80.

The residue, which is again collected in tanks 56 and 59, is allowed to flow into tank 12 by the venting of the tanks 56 and 59 in the manner above described, opening the valves 6I and allowing the liquid to ow through line 62 and line 19. Valve 1I is opened, allowing the liquid to now into tank 12.

The distillate collected in tank 89 contains approximately 78% fatty acids, 17% rosin acids and 5% esters and unsaponiables. The residue collected in tank 12 contains approximately 35% fatty acids, 56% rosin acids, and 9% esters and unsaponiables.

The liquid from tank 89 is again reprocessed by the opening of valve 82 allowing the liquid to ow into the line I3 and from there throughout the same cycle previously described.

The overhead, or distillate, is again collected in tanks 36 and 39 and the residue is again collected in tanks 56 and 59. In this instance, the receivers 36 and 39 are emptied into the storage tank 83 by venting the receivers 36 and 39 through air vents 31 and 49 as hereinbefore described, opening valves 54 and allowing the liquid to flow into line 11. Valve 841s opened, allowing the liquid to flow into tank 83.

The residue which has again been collected in receivers 56 and 59 is this time stored in storage tank I9. The transfer to tank I9 is accomplished v valves 6I and thus allowing the residue to flow by venting the tanks 56 and 59 through air vents 51v and 69 as hereinbefore described, opening through line 62 anclline 19. Valve 18 is then opened allowing the residue to flow into tank I9.

The distillate which is stored in tank 83 contains approximately 84% fatty acids, 9% rosin acids and 7% esters and unsapcniables. The residue which is stored in tank 89 contains approximately 60% fatty acids, 37% rosin acids and 3% esters and unsaponifiables.

The distillate which is contained in storage ltank 83 is recycled by opening valve 86, allowing the liquid distillate to flow through line I3, and from there through the same cycle as before. The distillate is again collected in tanks 36 and 39. The tanks 36 and 39 are emptied as above described by releasing the vacuum by opening the air vents 31 and 49 on tanks 36 and 39 respectively, opening the valves 54 allowing the distillate to flow into line 11. The distillate is collected in storage tank 81 by opening of valve 88 allowing the distillate to i'low from line 11 into tank 81.

The residue from this fourth vaporization is again collected in the receivers 56 and 59 as before described. The receivers 56 and 59 are emptied by first opening the air vents 51 and 69 respectively, and the valves 6I allowing the liquid in the tanks to flow through line 62 and line 19. The residue is now collected in storage tank 89 by opening valve 85 allowing the liquid to flow into the tank 89 from the line 19. The residue from this fourth vaporization is thus combined with the distillate from the second vaporization. The distillate which is thus collected in tank 81 contains approximately 89% fatty acids, 3.5% rosin acids and 7.5% unsaponifiables and nil esters. The residue collected in tank contains approximately 78% fatty acids,

17% rosin acids, nil unsaponiables and 5% esters.

The operations just described comprise the first integral step of the process, namely, the concentrating of rosin acids in the rened tall oil from the fatty acids and unsaponiables by four successive equilibrium vaporizations conducted at an absolute pressure of approximately 3 mm. Hg in the falling lm evaporator 26.

The distillate from the fourth vaporization is next subjected to the second part of the process to complete the separation of the unsaponiiiables from the fatty acids.

The distillate from storage tank 81 is removed through line 89 by pump 99. The distillate is pumped by pump 99 through line 9i to a steam heated heat exchanger 92 and through line 93 to a diphenyl-diphenyl oxide heated heat exchanger 94. 'Ihe heated distillate is then passed through lineA 95 to a fractionating column 96. The `distillate is fed into the fractionating column 96 at a point which approximates the middle of the column. The lower half of the fractionating column 96 constitutes a stripping section 96a, wherein the maximum pressure is less than 20 mm. Hg and preferably at about 15 mm., and the upper half of the fractionating column constitutes a rectifying section 96h, wherein the minimum pressure is less than 5 mm. Hg, and preferably is about 3mm. Hg. The function of the stripping section is to remove substantially all of the unsaponiables from the fatty and rosin acids, while that of the rectifying section is tol concentrate the unsaponiflables. The entire column 96 is packed with a porcelain packing material. Liquid introduced into the column, either through line 95 or as reflux, flows down the l1 column over the surface of the packing, countercurrent to the rising vapors. The packing Ainsures intimate contact between the liquid and vapor phases. Liquid reaching the bottom of the column is recirculated through line 91, pump 08 and line 99 to a falling film evaporator |00. The falling lm evaporator is identical except for size with the evaporator 26 and is heated by a mixture of diphenyl and diphenyl oxide introduced into the evaporator through line |03. Evaporator |00 serves only to heat the recirculated liquid. The temperature of the recirculated liquid is determined by a thermocouple |03a inserted in the lower portion of the evaporator |00. The thermocouple |03a in line |03b determines the iiow of heat transfer medium by controlling a valve |03c in line |03. The amount of liquid drawn off through the bottom of the column 96 is regulated by a liquid level control |02, associated with the fractionating column 96 and connected by means of a vline |0211 to an electrically operated valve |021).

The overhead vapors, viz., the vapors issuing from the top of the fractionating column 96, are conducted through line |04a to a condenser |04. A major portion of the condensed vapors from condenser |04 is returned to the fractionating column as reflux through lines |38 and |4|. The amount of liquid from the condenser |04 which is returned to the fractionating column 96 as reiiux is determined by a thermocouple |40 in the rectifying section 96h of the fractionating column 96. The thermocouple |40 regulates a valve |39a which is located between line |42 and line |38. If less liquid should be recycled as reflux, valve |39a is opened allowing the condensate from condenser |04 to iiow through line |42.

The uncondensed vapors from` condenser |04 are introduced into a cooler |05 where a portion of the vapors are condensed under a pressure of less than 5 mm. Hg. The non-condensed vvapors from cooler |05 areexhausted from the system through line |05a and a vacuum pump |05b at 3 mm. Hg absolute. The condensed vapors from cooler |05, together with the condensate from condenser |04 which is not reintroduced into the fractionating column as reux, pass through line |06 and through a U-tube liquid seal into receiver |08 which is maintained at an absolute pressure of 8 inches of mercury. When receiver |08 is filled, it is vented to the atmosphere through air vent |09 and the liquid is transferred to tank through line ||0. The contents of tank which contain a high percentage of unsaponiflables may be removed by opening a valve l la and collecting the liquid in a container I2. If desired, the contents of tank |I| may be pumped to a suitable storage vat (not shown) through line 3 by pump ||3a.

That portion of the liquid drawn off from the bottom of the fractionating column 96 through line 91 which is not returned to the fractionating column through the evaporator |00 may be pumped by pump 98 through line ||4 to a flash tower ||5. The flash tower H5 is operated at an absolute pressure of less than 5 mm. and preferably of 3 mm. Hg. The liquid introduced into the iiash tower through line ||4 is at an equilibrium temperature, which will ordinarily be around 450 F., corresponding to an absolute pressure of 10 to 20 mm. of mercury. The ash tower |5 is heated as necessary by a 'mixture of diphenyl and diphenyl `oxide introduced through line H6. The temperature of the ilash tower ||5 is regulated by a thermocouple ||5a located in the heating jacket of the tower ||5, and will, in general, be around 410 F. The amount of diphenyl-diphenyl oxide introduced into the jacket is controlled by the thermocouple controlled valve ||5b. The liquid entering the iiash tower ||5 through line ||4 is flashed into the Vapor phase by the sudden reduction of pressure.

The vapors thus obtained are passed from the flash tower ||5 through line to a condenser ||8 which ismaintained at a pressure of less than 5 mm. Hg. The condensed liquid in condenser ||8 is passed through line ||9 and through a cooler |20.

The cooled liquor from cooler |20 is passed through line |2| to receiver |24, this receiver being maintained at atmospheric pressure. Receiver |24 can be maintained at atmospheric pressure and still collect the condensate from condenser 3 by virtue of the difference in elevation between the two. The material from the accumulator |24 is withdrawn through a line |25 and pumped by pump |26 through line |21 and valve |28 into a storage tank |29.

The liquid which is not vaporized in the flash tower 5 is held in the lower portion of the, ash tower by a level control |43 which controls valve |33 which is located in a line |30. The purpose of the level control |43 is to insure the presence of liquid in a portion of the tower which is heated by the diphenyl-diphenyl oxide mixture introduced into the flash tower ||5 by line ||6. If the level of liquid in the flash tower falls below that indicated by device |43, valve |33 is closed preventing the fall of liquid in the heated portion. When the liquid level is above that of device |43, the liquid in the flash tower is drained through line |30 to cooler |3| and ,from the cooler I3| through line |32, valve |33 and line |34 to the receiver |35. When the receiver |35 is full, it is vented to atmospheric pressure by opening air vent |36, valve |35a is opened and the contents of tank |35 are drained through line |31 to tank 12 to be reprocessed.

Storage tank |29 thus receives a fatty acids fraction containing fatty acids, not more than 4% of rosin acids and not more than 1% ofunsaponifiables. Tank contains the unsaponiables and tank 64 contains the concentrated rosin acids. The concentrated rosin acids in tank 64 may be pumped through line 61 by pump 68 into line 60 to a pale rosin plant for further processing. The residue collected 'in receivers 56 and 59 may be pumped through line 62 and 62a by pump B2b into line 62o to a pale plant to be reprocessed rather than to the storage tanks. If the process is used in connection with a pale rosin plant to remove residual fatty acids from the plant residue, the residue may be pumped into tank .|39 through line |38, and drawn out of tank |39 through line |40 into line |3 for passing through the cycle above described.

The method of our invention thus enables the concentration of the rosin acids in a fraction containing only a small proportion of the fatty acids originally present, without, however, distilling more than a minor proportion of the rosin acids.

It will be understood that a greater or fewerl number of equilibrium vaporization steps than the four here specied may be used and that other changes in the method of our invention may be made within the scope of the appended claims. It is, therefore, not the purpose to limit the patent granted hereon other than necessitated by the scope of the appended claims.

We claim as our invention:

l. The process for the separation of fatty acids from rened tall voil containing fatty acids, rosin acids and unsaponifiables, which comprises preheating the tall oil in the absence of a solvent to a temperature less than the decomposition temperature of the rosin acids content of said tall oil, introducing the heated oil into an evaporating zone maintained at a pressure of less than mm. and a temperature of less than 266 C., removing from said evaporating zone a stream composed of vaporized lower boiling constituents rich in fatty acids and residual liquid rich in rosin acids, separating said vaporized lower boiling constituents from said residual rosin acidsrich liquid at a pressure of less than 5 mm., condensing said vaporized lower boiling constituents to obtain a fatty acids-rich fraction, recycling a portion of said residual liquid through said evaporation zone to vaporize the fatty acids contained therein, recycling said fatty acids-rich fraction through said preheating step, said evaporation zone, and said condensation step until a fraction is obtained which contains at least 85% fatty acids, and then heating said fraction containing at least 85% fatty acids to a temperature below the decomposition temperature of the said fraction, introducing the heated fraction into a fractionating zone having an upper rectifying section and a lower stripping section at a point between said sections, maintaining said stripping section at a pressure of less than 20 mm. to remove an unsaponiiiables-rich fraction and maintaining said rectifying section at a pressure of less than 5 mm. to concentrate said unsaponiables-rich fraction as overhead vapors, condensing and cooling said vapors from said rectifying section into a liquid fraction, returning a portion of the resulting liquid fraction as reflux to said rectifying section, recycling a portion of the fatty acids-rich liquid fraction from the stripping section through a heating zone maintained at a pressure of less than 20 mm. of mercury and a temperature of less than 260 C. back into said stripping section of said fractionating zone, introducing the remainder of said fatty acids-rich liquid fraction from said fractionating zone into a reduced pressure zone maintained at a pressure of less than 5 mm. pressure and a temperature less than 260 C., to vaporize the fatty acids in said liquid fraction, and condensing the resulting fatty acids vapors to obtain a product which contains at least 95% fatty acids.

2. A process for the separation of rened tall oil into a, fatty acids fraction, a rosin acids fraction and an unsaponiables fraction, which comprises preheating the tall oil to a temperature less than the decomposition temperature of the rosin acids content of said tall oil in the absence of solvent, introducing the heated oil into an evaporating zone maintained at a pressure less than 5 mm. and a temperature of less than 260 C., removing from said evaporating zone a stream composed of a vaporized fatty acids-rich fraction and residual rosin acids-rich liquid, separating said fatty acids-rich fraction from said rosin acids-rich liquid, condensing said vaporized fatty acids-rich fraction to obtain a liquid fatty acidsrich fraction and collecting said fatty acids-rich fraction, a portion of said rosin acids-rich liquid being recycled through said evaporation zone to further vaporize the fatty acids contained therein, said collected fatty acids-rich fraction be- A mm. of mercury absolute to remove a fatty acids-rich fraction substantially free of unsaponiflables and maintaining the top of said rectifying section at a pressure less than 5 mm. of mercury absolute to concentrate said unsaponiiiables-rich fraction as overhead vapors', condensing and cooling said vapors from said rectifying section, returning a portion of the resulting liquid fraction as reflux to said rectifying section, recycling a portion of the fatty acids-rich liquid fraction from the stripping section through a heating zone maintained at a pressure of less than 20 mm. of mercury absolute and a temperature of less than 260 C., said recycled portion being introduced into said stripping section of said fractionating zone, introducing the remainder of said fatty acids-rich liquid fraction from said fractionating zone into a reduced pressure zone maintained at a pressure of less than 5 mm. and a temperature less than 260 C. to vaporize the fatty acids in said liquid fraction, condensing the resulting fatty acids vapors to obtain a product containing at least fatty acids, not more than 4% rosin acids, and not more than 1% unsaponiiiables.

3. In the method of recovering fatty acids from a mixture of fatty acids, rosin acids and unsaponiables, the steps of introducing said mixture at an elevated temperature below 260 C. into a fractionating column at a point intermediate an upper rectifying section and a lower stripping section, the upper section of said fractionating column being maintained at an absolute pressure of about 3 mm. Hg and the lower section being maintained at an absolute pressure below 20 mm. Hg, withdrawing vapors from said upper section, condensing said vapors to provide a liquid rich in unsaponiables, returning a part of said liquid as reflux to said upper section, withdrawing liquid from said lower section, subjecting a portion of said last mentioned liquid to evaporation, supplying external heat to said liquid while in nlm form to heat and partially vaporize the same, leading the resulting vapors and liquid into said lower section, partially fiashing the remaining portion of said liquid withdrawn from said lower section into vapor at a pressure substantially less than that obtaining in said lower section and condensing said last mentioned vapor to obtain a substantially pure fatty acid condensate.

4. In a process of separating tall oil into a fatty acids product and a rosin acids product, the steps which comprise preheating the tall oil in the absence of a solvent to a temperature less than the decomposition temperature of the rosin acids components of said oil, introducing the heated oil into an evaporating zone maintained at a pressure of less than 5 mm. of mercury absolute and a temperature of less than 260 C., removing from a lower portion of said evaporating zone a. stream of both vaporized lower boiling constituents rich in fatty acids and residual liquids rich inunvaporized rosin acids,- separating said-vapor# ized lower boilingconstituents from saidzresidual resin` acids-rich liquid ina separate -1 zone valso maintained atapressure'of fless than:5-mm., condensingV said vaporized -lower boiling constituents to obtain'a fatty .acids-rich liquid fraction, collecting and recycling said fatty-acids-rich fraction through the same lsteps and in the same sequence hereinbeforevrecited until a'. fattyacidsrich fraction containing` at:'least"85% -of fatty acids by weight is obtained.

.References Cited kim thele of this patent UNITED STATES PATENTS Number Number I6 Name Date v Schultze Oct. 6, 1931 Gubelmann Feb. 23, 1932 Schulz Apr. 11, 1933 French Apr. 9, 1935 Potts et al. Sept. 15, 1936 Fawcett et al. Mar. 9, 1937 Frankel Jan. 10, 1939 Frankel Jan. 10, 1939 Van De Griendt Dec. 23, 1941 -Mills Mar. 3, 1942 Mills Mar. 3, 1942 Bogart et al. Feb. 16, 1943 Murphy Oct.V 31, 1944 FOREIGN PATENTS Country Date Sweden Jan. 19, 1943 

1. THE PROCESS FOR THE SEPARATION OF FATTY ACIDS FROM REFINED TALL OIL CONTAINING FATTY ACIDS, ROSIN ACIDS AND UNSAPONIFIABLES, WHICH COMPRISES PREHEATING THE TALL OIL IN THE ABSENCE OF A SOLVENT TO A TEMPERATURE LESS THAN THE DECOMPOSITION TEMPERATURE OF THE ROSIN ACIDS CONTENT OF SAID TALL OIL, INTRODUCING THE HEATED OIL INTO AN EVAPORATING ZONE MAINTAINED AT A PRESSURE OF LESS THAN 5 MM. AND A TEMPERATURE OF LESS THAN 260* C., REMOVING FROM SAID EVAPORATING ZONE A STREAM COMPOSED OF VAPORIZED LOWER BOILING CONSTITUENTS RICH IN FATTY ACIDS AND RESIDUAL LIQUID RICH IN ROSIN ACIDS, SEPARATING SAID VAPORIZED LOWER BOILING CONSTITUENTS FROM SAID RESIDUAL ROSIN ACIDSRICH LIQUID AT A PRESSURE OF LESS THAN 5 MM., CONDENSING SAID VAPORIZED LOWER BOILING CONSTITUENTS TO OBTAIN A FATTY ACIDS-RICH FRACTION, RECYCLING A PORTION OF SAID RESIDUAL LIQUID THROUGH SAID EVAPORATION ZONE TO VAPORIZE THE FATTY ACIDS-RICH FRACTION THEREIN, RECYCLING SAID FATTY ACIDS-RICH FRACTION THROUGH SAID PREHEATING STEP, SAID EVAPORATION ZONE, AND SAID CONDENSATION STEP UNTIL A FRACTION IS OBTAINED WHICH CONTAINS AT LEAST 85% FATTY ACIDS, AND THEN HEATING SAID FRACTION CONTAINING AT LEAST 85% FATTY ACIDS TO A TEMPERATURE BELOW THE DECOMPOSITION TEMPERATURE OF THE SAID FRACTION, INTRODUCING THE HEATED FRACTION INTO A FRACTIONATING ZONE HAVING AN UPPER RECTIFYING SECTION AND A LOWER STRIPPING SECTION AT A POINT BETWEEN SAID SECTIONS, MAINTAINING SAID STRIPPING SECTION AT A PRESSURE OF LESS THAN 20 MM. TO REMOVE AN UNSAPONIFIABLES-RICH FRACTION AND MAINTAINING SAID RECTIFYING SECTION AT A PRESSURE OF LESS THAN 5 MM. TO CONCENTRATE SAID UNSAPONIFIABLES-RICH FRACTION AS OVERHEAD VAPORS, CONDENSING AND COOLING SAID VAPORS FROM SAID RECTIFYING SECTION INTO A LIQUID FRACTION, RETURNING A PORTION OF THE RESULTING LIQUID FRACTION AS REFLUX TO SAID RECTIFYING SECTION RECYCLING A PORTION OF THE FATTY ACIDS-RICH LIQUID FRACTION FROM THE STRIPPING SEC- 